All electronic devices and circuits generate heat and thus require thermal management to improve reliability and prevent premature failure. The amount of heat output is equal to the power input, if there are no other energy interactions. There are several techniques for cooling electronic devices, including various styles of heat sinks, thermoelectric coolers, forced air systems and fans, heat pipes, and others.
Typical power electronic products contain numerous discrete sources of heat (e.g. power semiconductor switches, capacitors, and inductors) non-uniformly distributed within an enclosure. As a result, more complex cooling methods using dielectric fluids pumped by cooling loops and/or cold-plate based solutions have been required. For example, U.S. Pat. No. 6,016,007, describes a power electronics cooling apparatus which utilizes a dielectric fluid pumped through a cold plate to cool the power electronic semiconductors. This type of solution adds significantly to the cost of the product and it decreases the overall reliability.
Simpler cooling solutions exist for passive devices such as transformers. In U.S. Patent Publication No. US 2001/0032718A1, entitled System and Method for Cooling Transformers, there is described, among other things, a common practice for cooling transformers by a passively driven cooling fluid through an external heat exchanger. Since transformers comprise large, uniformly distributed heat sources (i.e. the transformer coils), generating a passively driven cooling loop through an external heat exchanger is relatively straight-forward. However, such less complex, passive cooling systems in power electronic devices has yet to be realized.